Powder coated with copper (i) oxide, and process for production thereof

ABSTRACT

Disclosed is a powder coated with copper (I) oxide, in which copper (I) oxide is adhered well, which can be dispersed well in a stain-proof coating, and which can impart high storage stability to a stain-proof coating. Also disclosed is a process for producing a powder coated with copper (I) oxide, which comprises the following steps: a surface treatment step of contacting a core material with at least one aqueous surface treatment solution selected from an aqueous solution of a tin salt, an aqueous solution of a silver salt and an aqueous solution of a palladium salt to produce a surface-treated product of the core material; an electrodeposition step of dispersing the surface-treated product of the core material in an aqueous electrolyte solution containing an electrolyte and an anti-oxidant agent, and electrodepositing copper (I) oxide on the surface of the surface-treated product of the core material by using metal copper as an anode to produce a powder coated with copper (I) oxide; and a water-washing step of washing the powder coated with copper (I) oxide with water to produce the desired powder coated with copper (I) oxide, wherein the aqueous electrolyte solution has a chlorine ion concentration of 20 to 200 g/L.

TECHNICAL FIELD

The present invention relates to new cuprous oxide preferred as anantifouling pigment and is a cuprous oxide-coated powder in which thesurface of a core material is coated with cuprous oxide, and a methodfor manufacturing the same.

BACKGROUND ART

Cuprous oxide has been known as an antifouling pigment from old timesand is formulated into a paint, which is used as a ship bottom paint toprevent the attachment of shells and algae in the sea. The cuprous oxidehas a true specific gravity as large as 6.0, and a problem of thecuprous oxide has been that when the cuprous oxide is formulated into aship bottom paint, the cuprous oxide settles due to a difference inspecific gravity between the vehicle and the cuprous oxide. In addition,because of a rise in the price of metal raw materials in recent years,the reduction of the amount of use has been a problem in the industry.

A method for decreasing specific gravity by coating the surface of acore material with cuprous oxide is considered as a method fordecreasing specific gravity. For example, Japanese Patent Laid-Open No.1-213368 (Patent Document 1) discloses a method for manufacturing acomposite pigment for an antifouling paint by performing electrolysisusing a liquid in which a powder comprising at least SiO₂ and/or Al₂O₃is suspended in an aqueous solution comprising chlorine ions, as theelectrolyte, and a copper plate as the anode.

Patent Document 1: Japanese Patent Laid-Open No. 1-213368 (CLAIMS)DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, a problem of a cuprous oxide-coated powder obtained by themanufacturing method described in Patent Document 1 has been that it haspoor practicality, for example, the adhesion of the cuprous oxide ispoor, the dispersibility in an antifouling paint is poor, and thestorage stability of the antifouling paint worsens.

Accordingly, it is an object of the present invention to provide acuprous oxide-coated powder in which the adhesion of cuprous oxide ishigh and which has good dispersibility in an antifouling paint andincreases the storage stability of the antifouling paint.

Means for Solving the Problems

The present inventors have diligently studied over and over to solve theabove problem in conventional art, and, as a result, found that in amethod for manufacturing a cuprous oxide-coated powder byelectrodepositing cuprous oxide on a core material and then performingwater-washing, (1) a cuprous oxide-coated powder in which the adhesionof the cuprous oxide is high and which has good dispersibility can beobtained by surface-treating the surface of the core material, using anaqueous solution of a specific metal salt, before electrodepositing thecuprous oxide on the core material, and (2) the cuprous oxide-coatedpowder obtained in such a manner has a small amount of soluble chlorineions and increased storage stability of an antifouling paint, and so on,leading to the completion of the present invention.

Specifically, the present invention (1) provides a cuprous oxide-coatedpowder comprising a core material and cuprous oxide coating the surfaceof the core material, characterized in that

a mass ratio of the core material/the cuprous oxide is 95/5 to 10/90,and

an amount of chlorine ions dissolved from the cuprous oxide-coatedpowder in water is 0.1% by mass or less with respect to the cuprousoxide-coated powder.

In addition, the present invention (2) provides a method formanufacturing a cuprous oxide-coated powder, characterized bycomprising:

a surface treatment step of contacting a core material with any one ortwo or more surface treatment aqueous solutions of an aqueous solutionof a stannous salt, an aqueous solution of a silver salt, and an aqueoussolution of a palladium salt to obtain a surface-treated core material;

an electrodeposition step of dispersing the surface-treated corematerial in an electrolytic aqueous solution containing an electrolyteand an antioxidant, and electrodepositing cuprous oxide on the surfaceof the surface-treated core material, using metal copper as an anode, toobtain a cuprous oxide-coated powder; and

a water-washing step of water-washing the cuprous oxide-coated powder toobtain a cuprous oxide-coated powder, wherein

the concentration of chlorine ions in the electrolytic aqueous solutionis 20 to 200 g/L.

ADVANTAGE OF THE INVENTION

The present invention can provide a cuprous oxide-coated powder in whichthe adhesion of cuprous oxide is high and which has good dispersibilityin an antifouling paint and increases the storage stability of theantifouling paint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron micrograph of a silica powder, which is a rawmaterial, in Example 1;

FIG. 2 is an electron micrograph of a cuprous oxide-coated powder B1before an adhesion test in Example 1;

FIG. 3 is an electron micrograph of the cuprous oxide-coated powder B1after the adhesion test in Example 1;

FIG. 4 is an electron micrograph of fly ash, which is a raw material, inExample 2;

FIG. 5 is an electron micrograph of a cuprous oxide-coated powder B2before an adhesion test in Example 2;

FIG. 6 is an electron micrograph of a silica stone powder, which is araw material, in Example 3;

FIG. 7 is an electron micrograph of a cuprous oxide-coated powder B3before an adhesion test in Example 3;

FIG. 8 is an electron micrograph of a polyethylene powder, which is araw material, in Example 4;

FIG. 9 is an electron micrograph of a cuprous oxide-coated powder B4before an adhesion test in Example 4;

FIG. 10 is an electron micrograph of a fused silica powder, which is araw material, in Example 5;

FIG. 11 is an electron micrograph of a cuprous oxide-coated powder B5before an adhesion test in Example 5;

FIG. 12 is an electron micrograph of a cuprous oxide-coated powder B6before an adhesion test in Comparative Example 1;

FIG. 13 is an electron micrograph of the cuprous oxide-coated powder B6after the adhesion test in Comparative Example 1;

FIG. 14 is an electron micrograph of a cuprous oxide-coated powder B7before an adhesion test in Comparative Example 2;

FIG. 15 is an electron micrograph of a cuprous oxide-coated powder B8before an adhesion test in Comparative Example 3;

FIG. 16 is an electron micrograph of aggregate particles of the cuprousoxide-coated powder B8 before the adhesion test in Comparative Example3;

FIG. 17 is a particle size distribution diagram of the silica powder,which is a raw material, in Example 1;

FIG. 18 is a particle size distribution diagram of the cuprousoxide-coated powder B1 before the adhesion test in Example 1;

FIG. 19 is a particle size distribution diagram of the fly ash, which isa raw material, in Example 2;

FIG. 20 is a particle size distribution diagram of the cuprousoxide-coated powder B2 before the adhesion test in Example 2;

FIG. 21 is a particle size distribution diagram of the silica stonepowder, which is a raw material, in Example 3;

FIG. 22 is a particle size distribution diagram of the cuprousoxide-coated powder B3 before the adhesion test in Example 3;

FIG. 23 is a particle size distribution diagram of the polyethylenepowder, which is a raw material, in Example 4;

FIG. 24 is a particle size distribution diagram of the cuprousoxide-coated powder B4 before the adhesion test in Example 4;

FIG. 25 is a particle size distribution diagram of the fused silicapowder, which is a raw material, in Example 5;

FIG. 26 is a particle size distribution diagram of the cuprousoxide-coated powder B5 before the adhesion test in Example 5;

FIG. 27 is a particle size distribution diagram of the cuprousoxide-coated powder B6 before the adhesion test in Comparative Example1;

FIG. 28 is a particle size distribution diagram of the cuprousoxide-coated powder B7 before the adhesion test in Comparative Example2; and

FIG. 29 is a particle size distribution diagram of the cuprousoxide-coated powder B8 before the adhesion test in Comparative Example3.

BEST MODE FOR CARRYING OUT THE INVENTION

The cuprous oxide-coated powder according to the present invention is acuprous oxide-coated powder comprising a core material and cuprous oxidecoating the surface of the core material, wherein

a mass ratio of the core material/the cuprous oxide is 95/5 to 10/90,and

an amount of chlorine ions dissolved from the cuprous oxide-coatedpowder in water is 0.1% by mass or less with respect to the cuprousoxide-coated powder.

The cuprous oxide-coated powder according to the present invention is acuprous oxide-coated powder comprising a core material and cuprous oxidecoating the surface of the core material, and the core material iscoated with the cuprous oxide.

Examples of the core material for the cuprous oxide-coated powderaccording to the present invention include silicic acid-containinginorganic compounds, alkaline earth metal compounds, alumina, andorganic compounds. Examples of the silicic acid-containing inorganiccompounds for the core material include crystalline silica, amorphoussilica, diatomaceous earth, various zeolites, talc, clay, fly ash, glassbeads, glass balloons, and shirasu balloons. Examples of the alkalineearth metal compounds for the core material include alkaline earth metalsalts, such as barium sulfate and calcium carbonate. Examples of theorganic compounds for the core material include thermoplastic resins andthermosetting resins, more specifically, polyethylene, polypropylene,acrylic resins, polystyrene, polyester, fluororesins, silicon resins,phenolic resins, urea resins, melamine resins, and epoxy resins.

In the cuprous oxide-coated powder according to the present invention,the mass ratio of the core material/the cuprous oxide is 95/5 to 10/90,and the mass ratio is appropriately selected in the above range,depending on the type of core material.

In the cuprous oxide-coated powder according to the present invention,the amount of chlorine ions dissolved in water from the cuprousoxide-coated powder when the cuprous oxide-coated powder is added towater is 0.1% by mass or less with respect to the cuprous oxide-coatedpowder. The chlorine ions dissolved from the cuprous oxide-coated powderin water are easily dissolved in an antifouling paint. Therefore, whenthe cuprous oxide-coated powder is formulated into a paint as a shipbottom paint, the gelation of the antifouling paint occurs and thestorage stability worsens if the amount of chlorine ions dissolved fromthe cuprous oxide-coated powder in water is larger than the above range.In the present invention, the amount of chlorine ions dissolved from thecuprous oxide-coated powder in water being 0.1% by mass or less withrespect to the cuprous oxide-coated powder refers to the following. Whenthe cuprous oxide-coated powder is added to water, and the amount ofchlorine ions dissolved in the water is measured, the value of (X/Y)×100is 0.1 or less, wherein Y (g) is the mass of the cuprous oxide-coatedpowder added, and X (g) is the amount of chlorine ions dissolved in thewater from the cuprous oxide-coated powder.

In the present invention, the amount of chlorine ions dissolved from thecuprous oxide-coated powder in water is a value measured by an ionchromatograph.

The cuprous oxide-coated powder according to the present invention ispreferably manufactured by a method for manufacturing a cuprousoxide-coated powder according to the present invention shown below.

The method for manufacturing a cuprous oxide-coated powder according tothe present invention is a method for manufacturing a cuprousoxide-coated powder, comprising:

a surface treatment step of contacting a core material with any one ortwo or more surface treatment aqueous solutions of an aqueous solutionof a stannous salt, an aqueous solution of a silver salt, and an aqueoussolution of a palladium salt to obtain a surface-treated core material;

an electrodeposition step of dispersing the surface-treated corematerial in an electrolytic aqueous solution containing an electrolyteand an antioxidant, and electrodepositing cuprous oxide on the surfaceof the surface-treated core material, using metal copper as an anode, toobtain a cuprous oxide-coated powder; and

a water-washing step of water-washing the cuprous oxide-coated powder toobtain a cuprous oxide-coated powder, wherein

the concentration of chlorine ions in the electrolytic aqueous solutionis 20 to 200 g/L.

The surface treatment step for the method for manufacturing a cuprousoxide-coated powder according to the present invention is the step ofcontacting a core material with a surface treatment aqueous solution toperform the surface treatment of the core material to obtain asurface-treated core material.

The core material for the method for manufacturing a cuprousoxide-coated powder according to the present invention is the same asthe core material for the cuprous oxide-coated powder according to thepresent invention.

When the core material for the cuprous oxide-coated powder according tothe present invention is a thermoplastic resin, a thermosetting resin,or the like, more specifically, polyethylene, polypropylene, an acrylicresin, polystyrene, polyester, a fluororesin, a silicon resin, aphenolic resin, a urea resin, a melamine resin, an epoxy resin, or thelike, the core material subjected to alkali washing and surfaceroughening with an acid can be used. In other words, the core materialmay be subjected to alkali washing and surface roughening with an acidbefore the surface treatment step for the method for manufacturing acuprous oxide-coated powder according to the present invention isperformed. Examples of the alkali used in alkali washing the corematerial for the cuprous oxide-coated powder according to the presentinvention include sodium hydroxide, sodium carbonate, sodiumorthosilicate, and sodium pyrophosphate. Examples of the acid used insurface roughening the core material for the cuprous oxide-coated powderaccording to the present invention with an acid include one selectedfrom sulfuric acid, nitric acid, phosphoric acid, chromic acid,hydrochloric acid, acetic acid, hydrofluoric acid, and the like, or amixed acid of two or more thereof.

The average particle diameter of the core material is preferably 0.5 to100 μm. If the average particle diameter of the core material is lessthan the above range, problems such as poor handling properties anddifficulty in solid-liquid separation tend to occur. On the other hand,if the average particle diameter of the core material is more than theabove range, problems such as poor dispersion stability in anantifouling paint and poor smoothness of the coating film tend to occur.

The outer shape of the core material is not particularly limited. Inaddition, the core material may be hollow particles or solid particles.

The surface treatment aqueous solution for the method for manufacturinga cuprous oxide-coated powder according to the present invention is anaqueous solution of a stannous salt, an aqueous solution of a silversalt, or an aqueous solution of a palladium salt, or a mixed aqueoussolution of a silver salt and a palladium salt. In the surface treatmentstep, the core material may be contacted only with one type of surfacetreatment aqueous solution, or the core material may be contacted withone surface treatment aqueous solution and then with another type ofsurface treatment aqueous solution.

Examples of the aqueous solution of a stannous salt for the surfacetreatment aqueous solution include aqueous solutions of stannoushalides, such as an aqueous solution of stannous fluoride and an aqueoussolution of stannous chloride, and an aqueous solution of stannoussulfate. Examples of the aqueous solution of a silver salt for thesurface treatment aqueous solution include aqueous solutions of silvernitrate, silver acetate, and silver sulfate. Examples of the aqueoussolution of a palladium salt according to the surface treatment aqueoussolution include an aqueous solution of palladium chloride.

The concentration of the stannous salt, the silver salt, or thepalladium salt in the surface treatment aqueous solution is preferably0.1 to 40 g/L, particularly preferably 0.5 to 30 g/L.

The surface treatment aqueous solution can contain hydrochloric acid andammonia water, as required.

The method for contacting the core material with the surface treatmentaqueous solution in the surface treatment step is not particularlylimited. Examples of the method include a method comprising adding thecore material to the surface treatment aqueous solution and stirringthem.

The temperature of the surface treatment aqueous solution in performingthe surface treatment step is not particularly limited and is preferably0 to 70° C., particularly preferably 10 to 50° C.

In the surface treatment step, the core material is contacted with thesurface treatment aqueous solution, and then, the core material isseparated from the surface treatment aqueous solution to obtain thesurface-treated core material. In the surface treatment step, the corematerial may be contacted only with one type of surface treatmentaqueous solution, or the core material may be contacted with two or moretypes of surface treatment aqueous solution, for example, the corematerial is contacted with one surface treatment aqueous solution andthen separated, and further contacted with another surface treatmentaqueous solution and separated.

Examples of the method for separating the core material from the surfacetreatment aqueous solution after performing surface treatment includeBuchner filtration and centrifugation. The surface-treated core materialseparated from the surface treatment aqueous solution can be dried asrequired.

The electrodeposition step for the method for manufacturing a cuprousoxide-coated powder according to the present invention is a step ofdispersing the surface-treated core material in an electrolytic aqueoussolution, and electrodepositing cuprous oxide on the surface of thesurface-treated core material, using metal copper as an anode, to obtaina cuprous oxide-coated powder (before water-washing).

The electrolytic aqueous solution for the method for manufacturing acuprous oxide-coated powder according to the present invention containsan electrolyte and an antioxidant.

The electrolyte for the electrolytic aqueous solution needs to havechlorine ions and is sodium chloride or potassium chloride.

The concentration of chlorine ions in the electrolytic aqueous solutionis 20 to 200 g/L, preferably 20 to 150 g/L. If the concentration ofchlorine ions in the electrolytic aqueous solution is less than theabove range, the electrodeposition rate is slow, and the operabilityworsens. On the other hand, if the concentration of chlorine ions in theelectrolytic aqueous solution is more than the above range, the amountof chlorine ions taken in the electrodeposited cuprous oxide increases,and the chlorine ions cannot be sufficiently removed even ifwater-washing is performed in the water-washing step.

Examples of the antioxidant for the electrolytic aqueous solutioninclude glycerin, citric acid, and saccharides.

The concentration of the antioxidant in the electrolytic aqueoussolution is preferably 0.3 to 60 g/L, particularly preferably 0.5 to 40g/L. If the concentration of the antioxidant in the electrolytic aqueoussolution is less than the above range, it tends to be difficult toobtain the effect of preventing the oxidation of the cuprous oxide. Onthe other hand, even if the concentration of the antioxidant in theelectrolytic aqueous solution is more than the above range, the effectof preventing the oxidation of the cuprous oxide is obtained, but theeffect reaches a maximum, and it is difficult to obtain the effectcorresponding to the concentration.

In the electrodeposition step, the amount of the surface-treated corematerial dispersed in the electrolytic aqueous solution is preferably 1to 80 g/L, particularly preferably 1 to 60 g/L, with respect to theelectrolytic aqueous solution. If the amount of the surface-treated corematerial dispersed in the electrolytic aqueous solution is less than theabove range, the efficiency of electrodeposition tends to worsen. On theother hand, if the amount of the surface-treated core material dispersedin the electrolytic aqueous solution is more than the above range, theconcentration of the core material in the electrolytic aqueous solutionis high, and therefore, the aggregation of the core material tends tooccur during electrodeposition.

In the electrodeposition step, metal copper is used as the anode, andusually, a metal copper plate is used. The purity of the metal copperfor the electrodeposition step may be 99% or more. In theelectrodeposition step, metal copper, SUS, or the like is used as thecathode, and usually, a metal copper plate, a SUS plate, or the like isused.

In the electrodeposition step, the cuprous oxide is electrodeposited onthe surface of the surface-treated core material by adding thesurface-treated core material to the electrolytic aqueous solution,stirring the electrolytic aqueous solution to disperse thesurface-treated core material, placing the anode and the cathode, andpassing an electric current with stirring.

The electrodeposition temperature in the electrodeposition in theelectrodeposition step is preferably 10 to 70° C. If theelectrodeposition temperature is less than the above range, theelectrodeposition rate tends to decrease. On the other hand, if theelectrodeposition temperature is more than the above range, thegeneration of gas accompanying the electrodeposition increases, and theadhesion between the cuprous oxide and the core material surface tendsto decrease.

The current density in the electrodeposition in the electrodepositionstep is 1 to 30 A/dm², preferably 1 to 10 A/dm². If the current densityis less than the above range, the time required for theelectrodeposition increases, and the operation efficiency tends toworsen. On the other hand, if the current density is more than the aboverange, chlorine ions taken in the electrodeposited cuprous oxide tendsto increase.

In the electrodeposition step, the coating amount of the cuprous oxideto coat the core material can be adjusted by electrodeposition time inthe electrodeposition. This coating amount of the cuprous oxide isappropriately adjusted depending on the type of core material and ispreferably an amount in which the mass ratio of the core material/thecuprous oxide is 95/5 to 10/90. The electrodeposition time in theelectrodeposition in the electrodeposition step is appropriatelyselected depending on the coating amount of the cuprous oxide and isusually, preferably 10 minutes to 4 hours.

In the electrodeposition step, after the electrodeposition is performed,the cuprous oxide-coated powder is separated from the electrolyticaqueous solution by Buchner filtration, centrifugation, or the like toobtain the cuprous oxide-coated powder (before water-washing). Thecuprous oxide-coated powder before water-washing obtained by performingthe electrodeposition step is also described as the cuprous oxide-coatedpowder (before water-washing).

The water-washing step for the method for manufacturing a cuprousoxide-coated powder according to the present invention is the step ofwater-washing the cuprous oxide-coated powder (before water-washing)obtained in the electrodeposition step to obtain a water-washed cuprousoxide-coated powder.

In the water-washing step, repulp washing is general as the method forwater-washing the cuprous oxide-coated powder. At this time, the slurryconcentration of the cuprous oxide-coated powder in a mixed slurry ofthe cuprous oxide-coated powder (before water-washing) and water is 5 to20% by mass, and the washing time is 10 minutes to 60 minutes. In thewater-washing step, warm water at 10 to 70° C. can also be used as thewash water.

In the water-washing step, the cuprous oxide-coated powder (beforewater-washing) is water-washed until the concentration of chlorine ionsin the wash water used for the washing is 0.1% or less. The presence ofthe chlorine ions in the wash liquid can be determined by taking thesupernatant liquid, dropping an aqueous solution of silver nitrate intothe supernatant liquid, and observing the state of cloudiness of thesupernatant liquid.

In the water-washing step, preferably, the cuprous oxide-coated powderis washed with wash water containing an antioxidant, because the coatingcuprous oxide can be prevented from being oxidized during thewater-washing step. In this case, examples of the antioxidant containedin the wash water include glycerin and saccharides. The concentration ofthe antioxidant in the wash water is preferably 0.3 to 60 g/L,particularly preferably 0.5 to 40 g/L.

In the water-washing step, after the cuprous oxide-coated powder (beforewater-washing) is water-washed, the cuprous oxide-coated powder afterthe water-washing is separated from the wash liquid and dried to obtainthe water-washed cuprous oxide-coated powder.

In the water-washing step, not only chlorine ions attached to thesurface of the coating layer of the coating cuprous oxide, but alsochlorine ions contained in the coating layer of the cuprous oxide can beremoved. Therefore, in the cuprous oxide-coated powder obtained byperforming the water-washing step, the content of chlorine ionsdissolved in an antifouling paint (hereinafter also described as solublechlorine ions) when the cuprous oxide-coated powder is dispersed in theantifouling paint is low.

The cuprous oxide-coated powder obtained by performing the method formanufacturing a cuprous oxide-coated powder according to the presentinvention is a cuprous oxide-coated powder in which the amount ofchlorine ions dissolved from the cuprous oxide-coated powder when thecuprous oxide-coated powder is added to water is 0.1% by mass or lesswith respect to the cuprous oxide-coated powder.

The chlorine ions dissolved from the cuprous oxide-coated powder whenthe cuprous oxide-coated powder is added to water are easily dissolvedin an antifouling paint. Therefore, when the cuprous oxide-coated powderis formulated into a paint as a ship bottom paint, the gelation of theantifouling paint occurs and the storage stability worsens if the amountof chlorine ions dissolved from the cuprous oxide-coated powder when thecuprous oxide-coated powder is added to water is larger than the aboverange.

In the cuprous oxide-coated powder according to the present invention,the amount of chlorine ions dissolved from the cuprous oxide-coatedpowder when the cuprous oxide-coated powder is added to water is 0.1% bymass or less with respect to the cuprous oxide-coated powder, andtherefore, the amount of soluble chlorine ions is small. Therefore, theantifouling paint is not easily gelled, and therefore, with the cuprousoxide-coated powder according to the present invention, an antifoulingpaint having excellent storage stability is obtained.

In the method for manufacturing a cuprous oxide-coated powder accordingto the present invention, the throwing power and adhesion of the cuprousoxide are improved by performing the surface treatment step, andtherefore, the adhesion of the coating layer of the cuprous oxideincreases, and a single powder of cuprous oxide and aggregates of thecuprous oxide-coated powder can be extremely reduced. Therefore, withthe method for manufacturing a cuprous oxide-coated powder according tothe present invention, a cuprous oxide-coated powder having gooddispersion stability in an antifouling paint is obtained. In the presentinvention, a single powder of cuprous oxide and aggregates of thecuprous oxide-coated powder being extremely reduced is found bycomparing the particle size distribution of the core material that is araw material in the method for manufacturing a cuprous oxide-coatedpowder according to the present invention, with the particle sizedistribution of the cuprous oxide-coated powder obtained by the methodfor manufacturing a cuprous oxide-coated powder according to the presentinvention.

In addition, in the method for manufacturing a cuprous oxide-coatedpowder according to the present invention, the surface of the corematerial is uniformly coated with the cuprous oxide, and therefore, inthe water-washing step, not only chlorine ions present on the surface ofthe coating layer of the cuprous oxide, but also chlorine ions containedin the coating layer of the cuprous oxide can be washed. Therefore, withthe method for manufacturing a cuprous oxide-coated powder according tothe present invention, a cuprous oxide-coated powder having a smallamount of soluble chlorine ions is obtained.

In other words, there are no aggregate particles such as fine particlesof cuprous oxide, which have been conventionally present and aredifficult to wash, in the present invention, and therefore, thecontained chlorine ions are removed.

Next, the present invention will be more specifically described byExamples, but these Examples are only illustrative and do not limit thepresent invention.

EXAMPLES Example 1 Surface Treatment Step

A silica powder (average particle diameter: 5 μm) (electron micrograph:FIG. 1) as a core material was dispersed in an aqueous solution of tinfluoride (1 g/L) followed by stirring, filtration, water-washing,dispersion in an aqueous solution of silver nitrate (1 g/L), stirring,filtration, water-washing, and drying to obtain a surface-treated corematerial A1.

(Electrodeposition Step and Water-Washing Step)

Then, 10 g of the surface-treated core material A1 was added to 1 L ofan electrolytic aqueous solution, and electrodes were placed. Anelectric current was passed for 36 minutes under the followingconditions, with stirring by a magnetic stirrer, to electrodepositcuprous oxide on the surface-treated core material A1. Then, theelectrolytic aqueous solution was filtered, and the filtered materialwas water-washed and then dispersed in an aqueous solution of glycerinfollowed by filtration and drying to obtain 21 g of a cuprousoxide-coated powder B1. The true specific gravity of the cuprousoxide-coated powder B1 was 3.1 g/cm³.

<Electrolytic Aqueous Solution>

Sodium chloride: 250 g/L (chlorine ion concentration: 152 g/L)

Glycerin: 10 g/L <Treatment Conditions>

Current density: 7 A/dm²Liquid temperature of electrolytic aqueous solution: 40° C.Electrodes: copper plates for both anode and cathode

(Performance Evaluation) <Surface Observation>

The cuprous oxide-coated powder B1 was observed with an electronmicroscope. An electron micrograph is shown in FIG. 2. As a result, itwas observed that the surface of the core material was evenly coatedwith cuprous oxide particles. In addition, the aggregation of thecuprous oxide-coated powder was hardly seen. In addition, a singlepowder of cuprous oxide was hardly seen.

<Particle Size Distribution Measurement>

The particle size distribution of the silica powder of the corematerial, which was a raw material, and the obtained cuprousoxide-coated powder B1 was measured. The particle size distribution ofthe silica powder of the core material is shown in FIG. 17, and theparticle size distribution of the cuprous oxide-coated powder B1 isshown in FIG. 18. With no fine powder portions seen, the shape of theparticle size distribution of the cuprous oxide-coated powder B1 wasalmost unchanged from the shape of the particle size distribution of thesilica powder of the core material, which was a raw material. Therefore,from these distribution diagrams, it is found that in the cuprousoxide-coated powder B1, the surface of the core material is uniformlycoated with the cuprous oxide particles. The particle size distributionmeasurement was performed by Microtrac, NIKKISO CO., LTD.

<Measurement of Amount of Chlorine Ions Dissolved in Water>

The amount of chlorine ions dissolved in water from the cuprousoxide-coated powder when the cuprous oxide-coated powder was added tothe water was measured by an ion chromatograph. As a result, the amountof chlorine ions dissolved from the cuprous oxide-coated powder in waterwas 0.05% by mass with respect to the cuprous oxide-coated powder. Themeasurement equipment was DX-320, and the column was AS12A. Na₂CO₃ andNaHCO₃ were used for the eluent.

<Adhesion Test of Cuprous Oxide>

The adhesion of the cuprous oxide-coated powder B1 was evaluated by thefollowing procedure. An electron micrograph after the adhesion test isshown in FIG. 3. As a result, the average value of the number ofparticles, from which the cuprous oxide was peeled, per field of viewwas 1 or less.

(1) The sample, zirconia beads, and toluene are placed in a container.(2) They are stirred by a stirring apparatus for 10 minutes.(3) After the stirring, the sample and the zirconia beads are separatedby a sieve.(4) The separated sample is filtered by a funnel.(5) The sample is subjected to natural drying.(6) The peeling state of the cuprous oxide particles is observed by anelectron microscope (×500, a magnification at which about 50 particlesare included in the field of view is selected).(7) 10 fields of view are observed at random, the number of peeledparticles in each field of view is counted, and the average value isobtained.

<Storage Stability of Antifouling Paint>

An antifouling paint was formulated using the cuprous oxide-coatedpowder B1, and allowed to stand for 36 days. The viscosity of theantifouling paint after the standing was measured to be 79 Ku, which wasalmost unchanged from the viscosity of the antifouling paint immediatelyafter the formulation, 78 Ku.

Example 2 Surface Treatment Step

Fly ash (average particle diameter: 41 μm) (electron micrograph: FIG. 4)as a core material was dispersed in an aqueous solution of silvernitrate (1 g/L) followed by stirring, filtration, water-washing, anddrying to obtain a surface-treated core material A2.

(Electrodeposition Step and Water-Washing Step)

Then, 10 g of the surface-treated core material A2 was added to 1 L ofan electrolytic aqueous solution, and electrodes were placed. Anelectric current was passed for 18 minutes under the followingconditions, with stirring by the magnetic stirrer, to electrodepositcuprous oxide on the surface-treated core material A2. Then, theelectrolytic aqueous solution was filtered, and the filtered materialwas water-washed and then dispersed in an aqueous solution of glycerinfollowed by filtration and drying to obtain 16 g of a cuprousoxide-coated powder B2. The true specific gravity of the cuprousoxide-coated powder B2 was 1.2 g/cm³.

<Electrolytic Aqueous Solution>

Sodium chloride: 200 g/L (chlorine ion concentration: 121 g/L)

Glycerin: 10 g/L <Treatment Conditions>

Current density: 7 A/dm²Liquid temperature of electrolytic aqueous solution: 30° C.Electrodes: copper plates for both anode and cathode

(Performance Evaluation) <Surface Observation>

The cuprous oxide-coated powder B2 was observed with the electronmicroscope. An electron micrograph is shown in FIG. 5. As a result, itwas observed that the surface of the core material was evenly coatedwith cuprous oxide particles. In addition, the aggregation of thecuprous oxide-coated powder was hardly seen. In addition, a singlepowder of cuprous oxide was hardly seen.

<Particle Size Distribution Measurement>

The particle size distribution of the fly ash of the core material,which was a raw material, and the obtained cuprous oxide-coated powderB2 was measured. The particle size distribution of the fly ash of thecore material is shown in FIG. 19, and the particle size distribution ofthe cuprous oxide-coated powder B2 is shown in FIG. 20. With no finepowder portions seen, the shape of the particle size distribution of thecuprous oxide-coated powder B2 was almost unchanged from the shape ofthe particle size distribution of the fly ash of the core material,which was a raw material. Therefore, from these distribution diagrams,it is found that in the cuprous oxide-coated powder B2, the surface ofthe core material is uniformly coated with the cuprous oxide particles.

<Measurement of Amount of Chlorine Ions Dissolved in Water>

The measurement of the amount of chlorine ions dissolved in water wasperformed by the same method as in Example 1. The amount of chlorineions dissolved from the cuprous oxide-coated powder in water was 0.04%by mass with respect to the cuprous oxide-coated powder.

<Adhesion Test of Cuprous Oxide>

The adhesion test of the cuprous oxide was performed by the same methodas in Example 1. The average value of the number of particles from whichthe cuprous oxide was peeled was 1 or less.

<Storage Stability of Antifouling Paint>

Operation was performed by the same method as in Example 1. Theviscosity of an antifouling paint after standing for 36 days was 74 Ku,which was almost unchanged from the viscosity of the antifouling paintimmediately after formulation, 72 Ku.

Example 3 Surface Treatment Step

A silica stone powder (average particle diameter: 32 μm) (electronmicrograph: FIG. 6) as a core material was dispersed in an aqueoussolution of tin fluoride (1 g/L) followed by stirring, filtration,water-washing, dispersion in an aqueous solution of palladium chloridecontaining hydrochloric acid (palladium chloride: 0.2 g/L, hydrochloricacid 1 ml/L), stirring, filtration, water-washing, and drying to obtaina surface-treated core material A3.

(Electrodeposition Step and Water-Washing Step)

Then, 10 g of the surface-treated core material A3 was added to 1 L ofan electrolytic aqueous solution, and electrodes were placed. Anelectric current was passed for 25 minutes under the followingconditions, with stirring by the magnetic stirrer, to electrodepositcuprous oxide on the surface-treated core material A3. Then, theelectrolytic aqueous solution was filtered, and the filtered materialwas water-washed and then dispersed in an aqueous solution of glycerinfollowed by filtration and drying to obtain 16 g of a cuprousoxide-coated powder B3. The true specific gravity of the cuprousoxide-coated powder B3 was 3.2 g/cm³.

<Electrolytic Aqueous Solution>

Sodium chloride: 200 g/L (chlorine ion concentration: 121 g/L)

Glycerin: 10 g/L <Treatment Conditions>

Current density: 5 A/dm²Liquid temperature of electrolytic aqueous solution: 50° C.Electrodes: copper plates for both anode and cathode

(Performance Evaluation) <Surface Observation>

The cuprous oxide-coated powder B3 was observed with the electronmicroscope. An electron micrograph is shown in FIG. 7. As a result, itwas observed that the surface of the core material was evenly coatedwith cuprous oxide particles. In addition, the aggregation of thecuprous oxide-coated powder was hardly seen. In addition, a singlepowder of cuprous oxide was hardly seen.

<Particle Size Distribution Measurement>

The particle size distribution of the silica stone powder of the corematerial, which was a raw material, and the obtained cuprousoxide-coated powder B3 was measured. The particle size distribution ofthe silica stone powder of the core material is shown in FIG. 21, andthe particle size distribution of the cuprous oxide-coated powder B3 isshown in FIG. 22. With no fine powder portions seen, the shape of theparticle size distribution of the cuprous oxide-coated powder B3 wasalmost unchanged from the shape of the particle size distribution of thesilica stone powder of the core material, which was a raw material.Therefore, from these distribution diagrams, it is found that in thecuprous oxide-coated powder B3, the surface of the core material isuniformly coated with the cuprous oxide particles.

<Measurement of Amount of Chlorine Ions Dissolved in Water>

The measurement of the amount of chlorine ions dissolved in water wasperformed by the same method as in Example 1. The amount of chlorineions dissolved from the cuprous oxide-coated powder in water was 0.02%by mass with respect to the cuprous oxide-coated powder.

<Adhesion Test of Cuprous Oxide>

The adhesion test of the cuprous oxide was performed by the same methodas in Example 1. The average value of the number of particles from whichthe cuprous oxide was peeled was 1 or less.

<Storage Stability of Antifouling Paint>

Operation was performed by the same method as in Example 1. Theviscosity of an antifouling paint after standing for 36 days was 76 Ku,which was almost unchanged from the viscosity of the antifouling paintimmediately after formulation, 74 Ku.

Example 4 Surface Treatment Step

A polyethylene powder (average particle diameter: 20 μm) (electronmicrograph: FIG. 8) as a core material was washed with an aqueoussolution of sodium hydroxide, then subjected to surface roughening witha mixed acid of chromic acid, sulfuric acid, and phosphoric acid, andthen dispersed in an aqueous solution of tin fluoride (1 g/L) followedby stirring, filtration, water-washing, dispersion in an aqueoussolution of silver nitrate (1 g/L), stirring, filtration, water-washing,and drying to obtain a surface-treated core material A4.

(Electrodeposition Step and Water-Washing Step)

Then, 10 g of the surface-treated core material A4 was added to 1 L ofan electrolytic aqueous solution, and electrodes were placed. Anelectric current was passed for 15 minutes under the followingconditions, with stirring by the magnetic stirrer, to electrodepositcuprous oxide on the surface-treated core material A4. Then, theelectrolytic aqueous solution was filtered, and the filtered materialwas water-washed and then dispersed in an aqueous solution of glycerinfollowed by filtration and drying to obtain 14.6 g of a cuprousoxide-coated powder B4. The true specific gravity of the cuprousoxide-coated powder B4 was 1.2 g/cm³.

<Electrolytic Aqueous Solution>

Sodium chloride: 250 g/L (chlorine ion concentration: 152 g/L)

Glycerin: 10 g/L <Treatment Conditions>

Current density: 7 A/dm²Liquid temperature of electrolytic aqueous solution: 30° C.Electrodes: copper plates for both anode and cathode

(Performance Evaluation) <Surface Observation>

The cuprous oxide-coated powder B4 was observed with the electronmicroscope. An electron micrograph is shown in FIG. 9. As a result, itwas observed that the surface of the core material was evenly coatedwith cuprous oxide particles. In addition, the aggregation of thecuprous oxide-coated powder was hardly seen. In addition, a singlepowder of cuprous oxide was hardly seen.

<Particle Size Distribution Measurement>

The particle size distribution of the polyethylene powder of the corematerial, which was a raw material, and the obtained cuprousoxide-coated powder B4 was measured. The particle size distribution ofthe polyethylene powder of the core material is shown in FIG. 23, andthe particle size distribution of the cuprous oxide-coated powder B4 isshown in FIG. 24. With no fine powder portions seen, the shape of theparticle size distribution of the cuprous oxide-coated powder B4 wasalmost unchanged from the shape of the particle size distribution of thepolyethylene powder of the core material, which was a raw material.Therefore, from these distribution diagrams, it is found that in thecuprous oxide-coated powder B4, the surface of the core material isuniformly coated with the cuprous oxide particles.

<Measurement of Amount of Chlorine Ions Dissolved in Water>

The measurement of the amount of chlorine ions dissolved in water wasperformed by the same method as in Example 1. The amount of chlorineions dissolved from the cuprous oxide-coated powder in water was 0.02%by mass with respect to the cuprous oxide-coated powder.

<Adhesion Test of Cuprous Oxide>

The adhesion test of the cuprous oxide was performed by the same methodas in Example 1. The average value of the number of particles from whichthe cuprous oxide was peeled was 1 or less.

<Storage Stability of Antifouling Paint>

Operation was performed by the same method as in Example 1. Theviscosity of an antifouling paint after standing for 36 days was 80 Ku,which was almost unchanged from the viscosity of the antifouling paintimmediately after formulation, 78 Ku.

Example 5 Surface Treatment Step

A fused silica powder (amorphous, average particle diameter: 20 μm)(electron micrograph: FIG. 10) as a core material was alkali-washed withan aqueous solution of sodium hydroxide, subjected to surface rougheningwith hydrofluoric acid, and then dispersed in an aqueous solution of tinfluoride (1 g/L) followed by stirring, filtration, water-washing,dispersion in an aqueous solution of silver nitrate (1 g/L), stirring,filtration, water-washing, and drying to obtain a surface-treated corematerial A5.

(Electrodeposition Step and Water-Washing Step)

Then, 10 g of the surface-treated core material AS was added to 1 L ofan electrolytic aqueous solution, and electrodes were placed. Anelectric current was passed for 15 minutes under the followingconditions, with stirring by the magnetic stirrer, to electrodepositcuprous oxide on the surface-treated core material A5. Then, theelectrolytic aqueous solution was filtered, and the filtered materialwas water-washed and then dispersed in an aqueous solution of glycerinfollowed by filtration and drying to obtain 14.3 g of a cuprousoxide-coated powder B5. The true specific gravity of the cuprousoxide-coated powder B5 was 2.8 g/cm³.

<Electrolytic Aqueous Solution>

Sodium chloride: 250 g/L (chlorine ion concentration: 152 g/L)

Glycerin: 10 g/L <Treatment Conditions>

Current density: 7 A/dm²Liquid temperature of electrolytic aqueous solution: 30° C.Electrodes: copper plates for both anode and cathode

(Performance Evaluation) <Surface Observation>

The cuprous oxide-coated powder B5 was observed with the electronmicroscope. An electron micrograph is shown in FIG. 11. As a result, itwas observed that the surface of the core material was evenly coatedwith cuprous oxide particles. In addition, the aggregation of thecuprous oxide-coated powder was hardly seen. In addition, a singlepowder of cuprous oxide was hardly seen.

<Particle Size Distribution Measurement>

The particle size distribution of the fused silica powder of the corematerial, which was a raw material, and the obtained cuprousoxide-coated powder B5 was measured. The particle size distribution ofthe fused silica powder of the core material is shown in FIG. 25, andthe particle size distribution of the cuprous oxide-coated powder B5 isshown in FIG. 26. With no fine powder portions seen, the shape of theparticle size distribution of the cuprous oxide-coated powder B5 wasalmost unchanged from the shape of the particle size distribution of thefused silica powder of the core material, which was a raw material.Therefore, from these distribution diagrams, it is found that in thecuprous oxide-coated powder B5, the surface of the core material isuniformly coated with the cuprous oxide particles.

<Measurement of Amount of Chlorine Ions Dissolved in Water>

The measurement of the amount of chlorine ions dissolved in water wasperformed by the same method as in Example 1. The amount of chlorineions dissolved from the cuprous oxide-coated powder in water was 0.03%by mass with respect to the cuprous oxide-coated powder.

<Adhesion Test of Cuprous Oxide>

The adhesion test of the cuprous oxide was performed by the same methodas in Example 1. The average value of the number of particles from whichthe cuprous oxide was peeled was 1 or less.

<Stability of Antifouling Paint>

Operation was performed by the same method as in Example 1. Theviscosity of an antifouling paint after standing for 36 days was 78 Ku,which was almost unchanged from the viscosity of the antifouling paintimmediately after formulation, 76 Ku.

Comparative Example 1 Electrodeposition Step and Water-Washing Step

10 g of the silica powder (average particle diameter: 5 μm) used inExample 1, as a core material, was added to 1 L of an electrolyticaqueous solution, and electrodes were placed. An electric current waspassed for 36 minutes under the following conditions, with stirring bythe magnetic stirrer, to electrodeposit cuprous oxide on the corematerial. Then, the electrolytic aqueous solution was filtered, and thefiltered material was water-washed and then dispersed in an aqueoussolution of glycerin followed by filtration and drying to obtain 21 g ofa cuprous oxide-coated powder B6. The true specific gravity of thecuprous oxide-coated powder B6 was 3.1 g/cm³.

<Electrolytic Aqueous Solution>

Sodium chloride: 400 g/L (chlorine ion concentration: 243 g/L)

Glycerin: 10 g/L <Treatment Conditions>

Current density: 7 A/dm²Liquid temperature of electrolytic aqueous solution: 40° C.Electrodes: copper plates for both anode and cathode

(Performance Evaluation) <Surface Observation>

The cuprous oxide-coated powder B6 was observed with the electronmicroscope. An electron micrograph is shown in FIG. 12. As a result, itwas observed that the surface of the core material was sparsely coatedwith cuprous oxide particles. In addition, the aggregation of thecuprous oxide-coated powder was seen. In addition, a single powder ofcuprous oxide was seen.

<Particle Size Distribution Measurement>

The particle size distribution of the obtained cuprous oxide-coatedpowder B6 was measured. The particle size distribution of the cuprousoxide-coated powder B6 is shown in FIG. 27. There were more fineportions in the particle size distribution of the cuprous oxide-coatedpowder B6 than in the particle size distribution of the silica powder ofthe core material, which was a raw material (FIG. 17). Therefore, fromthese distribution diagrams, it is found that in the cuprousoxide-coated powder B6, the surface of the core material is notuniformly coated with the cuprous oxide particles, and aggregates of thecuprous oxide-coated powder are present.

<Measurement of Amount of Chlorine Ions Dissolved in Water>

The measurement of the amount of chlorine ions dissolved in water wasperformed by the same method as in Example 1. The amount of chlorineions dissolved from the cuprous oxide-coated powder in water was 0.20%by mass with respect to the cuprous oxide-coated powder.

<Adhesion Test of Cuprous Oxide>

The adhesion test of the cuprous oxide was performed by the same methodas in Example 1. An electron micrograph is shown in FIG. 13. As aresult, the peeling of the cuprous oxide particles was seen in allfields of view.

<Storage Stability of Antifouling Paint>

Operation was performed by the same method as in Example 1. Theviscosity of an antifouling paint after standing for 36 days was 99 Ku,which was higher than the viscosity of the antifouling paint immediatelyafter formulation, 76 Ku.

Comparative Example 2 Electrodeposition Step and Water-Washing Step

10 g of the fly ash (average particle diameter: 41 μm) used in Example2, as a core material, was added to 1 L of an electrolytic aqueoussolution, and electrodes were placed. An electric current was passed for25 minutes under the following conditions, with stirring by the magneticstirrer, to electrodeposit cuprous oxide on the core material. Then, theelectrolytic aqueous solution was filtered, and the filtered materialwas water-washed and then dispersed in an aqueous solution of glycerinfollowed by filtration and drying to obtain 16 g of a cuprousoxide-coated powder B7. The true specific gravity of the cuprousoxide-coated powder B7 was 3.2 g/cm³.

<Electrolytic Aqueous Solution>

Sodium chloride: 200 g/L (chlorine ion concentration: 121 g/L)

Glycerin: 10 g/L <Treatment Conditions>

Current density: 5 A/dm²Liquid temperature of electrolytic aqueous solution: 50° C.Electrodes: copper plates for both anode and cathode

(Performance Evaluation) <Surface Observation>

The cuprous oxide-coated powder B7 was observed with the electronmicroscope. An electron micrograph is shown in FIG. 14. As a result, itwas observed that the surface of the core material was sparsely coatedwith cuprous oxide particles. In addition, the aggregation of thecuprous oxide-coated powder was seen. In addition, a single powder ofcuprous oxide was seen.

<Particle Size Distribution Measurement>

The particle size distribution of the obtained cuprous oxide-coatedpowder B7 was measured. The particle size distribution of the cuprousoxide-coated powder B7 is shown in FIG. 28. There were more fineportions in the particle size distribution of the cuprous oxide-coatedpowder B7 than in the particle size distribution of the fly ash of thecore material, which was a raw material (FIG. 19). Therefore, from thesedistribution diagrams, it is found that in the cuprous oxide-coatedpowder B7, the surface of the core material is not uniformly coated withthe cuprous oxide particles, and the aggregation of the cuprousoxide-coated powder is present.

<Measurement of Amount of Chlorine Ions Dissolved in Water>

The measurement of the amount of chlorine ions dissolved in water wasperformed by the same method as in Example 1. The amount of chlorineions dissolved from the cuprous oxide-coated powder in water was 0.03%by mass with respect to the cuprous oxide-coated powder.

<Adhesion Test of Cuprous Oxide>

The adhesion test of the cuprous oxide was performed by the same methodas in Example 1. The peeling of the cuprous oxide particles was seen inall fields of view.

<Storage Stability of Antifouling Paint>

Operation was performed by the same method as in Example 1. Theviscosity of an antifouling paint after standing for 36 days was 81 Ku,which was almost unchanged from the viscosity of the antifouling paintimmediately after formulation, 80 Ku.

Comparative Example 3 Electrodeposition Step and Water-Washing Step

10 g of the silica stone powder (average particle diameter: 32 μm) usedin Example 3, as a core material, was added to 1 L of an electrolyticaqueous solution, and electrodes were placed. An electric current waspassed for 25 minutes under the following conditions, with stirring bythe magnetic stirrer, to electrodeposit cuprous oxide on the corematerial. Then, the electrolytic aqueous solution was filtered, and thefiltered material was water-washed and then dispersed in an aqueoussolution of glycerin followed by filtration and drying to obtain 16 g ofa cuprous oxide-coated powder B8. The true specific gravity of thecuprous oxide-coated powder B8 was 3.2 g/cm³.

<Electrolytic Aqueous Solution>

Sodium chloride: 400 g/L (chlorine ion concentration: 243 g/L)

Glycerin: 10 g/L <Treatment Conditions>

Current density: 5 A/dm²Liquid temperature of electrolytic aqueous solution: 50° C.Electrodes: copper plates for both anode and cathode

(Performance Evaluation) <Surface Observation>

The cuprous oxide-coated powder B8 was observed with the electronmicroscope. An electron micrograph is shown in FIG. 15. As a result, itwas observed that the surface of the core material was sparsely coatedwith cuprous oxide particles. In addition, the aggregation of thecuprous oxide-coated powder was seen (FIG. 16). In addition, a singlepowder of cuprous oxide was seen.

<Particle Size Distribution Measurement>

The particle size distribution of the obtained cuprous oxide-coatedpowder B8 was measured. The particle size distribution of the cuprousoxide-coated powder B8 is shown in FIG. 29. There were more fineportions in the particle size distribution of the cuprous oxide-coatedpowder B8 than in the particle size distribution of the silica stonepowder of the core material, which was a raw material. Therefore, fromthese distribution diagrams, it is found that in the cuprousoxide-coated powder B8, the surface of the core material is notuniformly coated with the cuprous oxide particles, and the aggregationof the cuprous oxide-coated powder is present.

<Measurement of Amount of Chlorine Ions Dissolved in Water>

The measurement of the amount of chlorine ions dissolved in water wasperformed by the same method as in Example 1. The amount of chlorineions dissolved from the cuprous oxide-coated powder in water was 0.15%by mass with respect to the cuprous oxide-coated powder.

<Adhesion Test of Cuprous Oxide>

The adhesion test of the cuprous oxide was performed by the same methodas in Example 1. The peeling of the cuprous oxide particles was seen inall fields of view.

<Storage Stability of Antifouling Paint>

Operation was performed by the same method as in Example 1. Theviscosity of an antifouling paint after standing for 36 days was 95 Ku,which was higher than the viscosity of the antifouling paint immediatelyafter formulation, 80 Ku.

TABLE 1 Throwing Solubility Paint power Adhesion Dispersibility Cl (%)stability Example 1 ∘ ∘ ∘ 0.05 ∘ Example 2 ∘ ∘ ∘ 0.04 ∘ Example 3 ∘ ∘ ∘0.02 ∘ Example 4 ∘ ∘ ∘ 0.02 ∘ Example 5 ∘ ∘ ∘ 0.03 ∘ Comparative x x x0.20 x Example 1 Comparative x x x 0.03 ∘ Example 2 Comparative x x x0.15 x Example 3

In Table 1, for the throwing power, a case where the state ofelectrodeposition of the cuprous oxide particles on the core materialwas whole is “◯,” and a case where the state of electrodeposition waspartial is “x.” For the adhesion, a case where the average value of thenumber of particles in which the cuprous oxide particles were peeledfrom the core material was 1 or less is “◯,” and a case where theaverage value of the number of particles was more than 1 is “x.” For thedispersibility, a case where there were no aggregate particles is “◯,”and a case where there were aggregate particles is “x.” For the paintstability, a case where the change in the viscosity of the paint wasless than 10% after a lapse of 36 days is “◯,” and a case where thechange in the viscosity was 10% or more is “x.”

1. A cuprous oxide-coated powder comprising a core material and cuprousoxide coating the surface of the core material, wherein a mass ratio ofthe core material/the cuprous oxide is 95/5 to 10/90, and an amount ofchlorine ions dissolved from the cuprous oxide-coated powder in water is0.1% by mass or less with respect to the cuprous oxide-coated powder. 2.The cuprous oxide-coated powder according to claim 1, wherein the corematerial is a silicic acid-containing inorganic compound.
 3. The cuprousoxide-coated powder according to claim 1, wherein the core material isan alkaline earth metal compound.
 4. The cuprous oxide-coated powderaccording to claim 1, wherein the core material is an organic compound.5. The cuprous oxide-coated powder according to claim 1, wherein thecore material is alumina.
 6. A method for manufacturing a cuprousoxide-coated powder, comprising: a surface treatment step of contactinga core material with any one or two or more surface treatment aqueoussolutions of an aqueous solution of a stannous salt, an aqueous solutionof a silver salt, and an aqueous solution of a palladium salt to obtaina surface-treated core material; an electrodeposition step of dispersingthe surface-treated core material in an electrolytic aqueous solutioncontaining an electrolyte and an antioxidant, and electrodepositingcuprous oxide on the surface of the surface-treated core material, usingmetal copper as an anode, to obtain a cuprous oxide-coated powder; and awater-washing step of water-washing the cuprous oxide-coated powder toobtain a cuprous oxide-coated powder, wherein the concentration ofchlorine ions in the electrolytic aqueous solution is 20 to 200 g/L. 7.The method for manufacturing a cuprous oxide-coated powder according toclaim 6, wherein the surface treatment aqueous solution is any one ortwo or more of an aqueous solution of tin fluoride, an aqueous solutionof silver nitrate, and an aqueous solution of palladium chloride.
 8. Themethod for manufacturing a cuprous oxide-coated powder according toclaim 6, wherein the electrolyte is sodium chloride.
 9. The method formanufacturing a cuprous oxide-coated powder according to claim 6,wherein the antioxidant is glycerin.
 10. The method for manufacturing acuprous oxide-coated powder according to claim 6, wherein thewater-washing step is performed by washing the cuprous oxide-coatedpowder with wash water containing an antioxidant.